Modify PercentTolerance.__str__ to only include the marginal percentage in the description if marginal_percent is not None.

PiperOrigin-RevId: 908371025

Author: OpenHTF Owners

openhtf/util/validators.py

@@ -498,8 +498,12 @@ def is_marginal(self, value) -> bool:
               self.marginal_maximum <= value < self.maximum)
 
   def __str__(self) -> str:
-    return "'x' is within {}% of {}. Marginal: {}% of {}".format(
-        self.percent, self.expected, self.marginal_percent, self.expected)
+    string_parts = [(f"'x' is within {self.percent}% of {self.expected}.")]
+    if self.marginal_percent is not None:
+      string_parts.append(
+          f'Marginal: {self.marginal_percent}% of {self.expected}'
+      )
+    return ' '.join(string_parts)
 
   def __eq__(self, other) -> bool:
     return (isinstance(other, type(self)) and

test/util/validators_test.py

@@ -314,11 +314,17 @@ def test_not_equals_when_not_equivalent(self):
     for validator in [validator_b, validator_c, validator_d]:
       self.assertNotEqual(validator_a, validator)
 
-  def test_string_representation_does_not_raise(self):
-    validator_a = validators.WithinPercent(expected=100, percent=10)
-    str(validator_a)
-    # Check that we constructed a usable validator.
-    self.assertTrue(validator_a(100))
+  def test_string_representation_without_marginal_percent(self):
+    validator = validators.WithinPercent(expected=100, percent=10)
+    self.assertEqual(str(validator), "'x' is within 10% of 100.")
+
+  def test_string_representation_with_marginal_percent(self):
+    validator = validators.WithinPercent(
+        expected=100, percent=10, marginal_percent=5
+    )
+    self.assertEqual(
+        str(validator), "'x' is within 10% of 100. Marginal: 5% of 100"
+    )
 
   def test_is_deep_copyable(self):
     validator_a = validators.WithinPercent(expected=100, percent=10)